My doc thought it was originally RLS also but I had it all day long not really at night unless it was just continuing from the day. It's a pain that very hard to describe, sometimes a twitchy itchy feeling sometimes it really kicks in. Sometimes its a very deep pain like at the bone then other times it just annoying crawly feeling. Sometimes it only goes to my knees and other times it goes from my sit bones right to my toes. Sounds alot like rls doesnt it? My rheumy gave me stretches to do which I used to do when I ran and it helps alittle. You lay on your back and bring both legs up and cross one over at the knee so it looks like the number 4 and SLOWLY pull back and he told me to SLOWLY roll from side to side from my waist and then I can really feel it. But my pain is in the backs of my thighs not the front so that may not help you. This like everything else with AS is somethimes it is this way sometimes not. You know it cant be easy...
Angie